Method of producing seamless drawn tubes and other tubular articles



P. OTTO METHO 0F PRODUCING SEAMLESS DRAWN TUBES AND OTHER TUBULAH ARTICLES May 2l, 1935.

Filed March 5. 1952 1;...temd May 21,1935 y 2,002,415 l lmuri-:D STATES 'PATENT 'OFFICE' N METHOD OF PROUCING SEAMLESS DRAW.

TUBES AND OTHER TUBULAR ARTICLES Peter Otto, Dusseldorf-Oberkassel,v Germany Application March 5, 1932, serial No. 5971121 In Great Britain March 19, 1931 e 2 claims. (c1. 29-156) My invention relates to-an improved method of ing additional difficulties, so that the push bench producing seamless tubes and other 'tubular arprocess is very expensive for several reasons. ticles; in extension of the'method also sheet plates According tothe invention hollow Ibodies proor plates can be produced out of the tubes. duced by the known centrifugal casting method 5 y The 'so-called push benchfprocess for the pro-- are used instead of solid cast ingots which have 5 duction of seamless tubes particularly of` iron been forged or rolled into billets and which then and steel is coming more and more into favour. vare punched. By this method tubes with both This method is executed as followsr--f-Ay rolled ends generally openv are obtained and it will, billet of square or other section is punched in therefore, be necessary to close onef end by hamlongitudinal direction of the billet and in red hot 'mering or the like. The hollow bodies produced 10 condition by a mandrel until a short solid end reby the centrifugal casting process have the admains. 'I'he sleeve thus obtained, the one end vantage that they can be made into long lengths of which is closed, is put on a mandrel bar and with comparatively thin walls without diilculty then, by means of the push bench, pushed through and it is therefore notnecessary to reduceA the a series of die rings which produce a longer, but wall thickness to-'such an extent as with thickl5 'thinner walled sleeve. This sleeve is still `closed walled sleeves. The operation of the push bench Y at one end by the solid remaining portionvand is, therefore, greatly simplified; the pushl benches together with the mandrel it is passed through a ,-are short and take up less space, are comparatively polishing mill which smoothes it down inside and` cheap and need not be so powerful. The tubes, 2'0 outside to its required thickness and releases `it therefore, are produced with'greater exactitude,in A20 from the mandrel bar. 'I'he latter is then withless time and therefore at less expense. In addidrawn, whereupon the solid end is cut off leavtion, the hollow-bodies obtained by the centrifu ing the required tube. gal casting method are cheap, due t'o the fact that A Medium-size tubes only are produced by th no waste material is obtained and above allv are method which, besides, hasI many disadvantages. absolutely.' symmetrical, so that they are much 25 Producing billets is not a simple operation. They more suitable for thepllsh bench process than bilare cast as solid ingots and forged or rolled into lets punched under pressure. Further, by saving the required section of the billet. Billets of dethe expense of the cumbersome and dear punch sired length are then cut off and once more heated presses, the cost of production of the tubes is j in a furnace. greatly reduced.

` The punching of the billets requires expensive The devices required for carrying the new presses and accumulators with large holding camethod into effect are shown as examples in ',pacities, but the most difficult operation is to the annexed drawing. schematically shown punch the billet exactly in the centre. If the are in A'35 punch is not set exactly in the centre or if the Fig. 1 a vertical -axial longitudinal section 35 punching has commencedconcentrically but the through. a centrifugal casting mould lor drum, punch mandrel has notgone quite straight, for Fig. 2 a. cross section through this mould or example due toan unequal heating of the billet, drum, i' and a sloping bore has thus resulted, such bil- Fig. 3 a longitudinal section through the tubu- '40 lets are-useless for further operations'. lar body produced in the centrifugal casting 40 I'he latest artA requires Very long tubes. In mould or drum, order to produce them, the sleeves obtained from-x Fig. 4 a cross section of the same,

the billets are to have very thick, walls to contain l Fig. 5 a longitudinal section through another sufllcient metal for the stretching out process. ,form of centrifugalcasting drum, a These thick walls must gradually be reduced in Fig. 6 a diagrammatical -sectional view of the 45 the push bench, for which purpose the sleeve must principal parts of a push bench, namely the be passed throughea. large'number of diev rings in mandrel bar andthe die rings, y

order to obtain the required long tube with Fig. 7 the same diagrammatical sectional view, thinned-out wall. The push benches, therefore, but the die rings substituted by rollers,

50 are very long and occupyalarge amount of space.. Figs. 8 and 9, sectionalfview of the Figs. 1 5c In addition it takes a comparatively long time to andl 2, metalbeing poured into the casting drum pass all the rings, so that the tube is cooled down in various layers. l l

to a great extent and thus very strong and pow- The method upon which the invention is basedv eriul push benches are necessary. Further, the is as followszj I long mandrel bars required are easily bent, caus- At first a tubular body a 'is obtained by the 55 centrifugal casting process. The device required for this purpose substantially consists in a comparatively long cylindrical ndrum b, the bottoms b1 of which have centrical openings cv and are removable. The drum is revolvably carried on.

rollers d. The rotation is d one by any suitable means not shown in drawing. If into said drum,

Whilst it revolves at a sufliciently high speed,l

. length of the drum, but also over the entire lso inner wall of, same in a uniform thickness, thus forming the cylindrical hollow body aif the rotation of the drum is continued so long until the metal poured in is suiiiciently solidified.

For the object in question it is necessary for the hollow .body a obtained to be closed at one end. This can be done by any suitable means after the casting process, also in that way that the casting drum b is being closed up by a movable bottom or piston disc g and by pushing this disc 4inwards under corresponding power, at a time when the metal poured in is not liquid any more but still red hot, that means plastic and formative.4 'The disc g moving inwards, in this instance pushes the metal in front of it thus -that it is compressed inwards anci by that forms a wall h. The tubular body a1 thus is still open at one end only. With this opening it is pushed on a mandrel bar z'of a push bench which isA mandrel bar i is being moved in the direction of the arrow, the body travels successively through the ring openings whereby its outside diameter is reduced and its length increased. Thereby the body va2 is obtained.v Owing to the pressure of the rings lc this body a2' sticks rmly upon the mandrel bar z'. In-order to release it from the mandrel bar, the body a2 together with the man drel bar z' is passed through a so-called polishing millthe rolls of which smooth the outside of the tubular body and at the same time slightly reduce its wall thickness,` so that thus the body is releasedfrom the mandrel bar. The

latter then can easily be drawn out of the tubular body a2. Byvthereupon cutting off the'solid end of the body a2, by means of a hot saw or the like. a iinished tube open at both ends is being ob- Itained. 'This tube may be subjected still to further treatmentin suitable rolling mills, such as -reducing millf and expanding mill, in order to get itto/the 'desired size and length; on the reducing mill it is being reduced and on the expanding mill expanded in diameter.

The new method embodies great advantages as compared to the methods employed hitherto.

` The centrifugal casting process is no dearer than the usual method of casting ingts. The forging or rolling of ingots into squarefbillets is dispensed with. The closing o f theone end of the centrify the 'waste which is prevalent in the case of asymmetric punched billets is avoided. l The long lengths and thin walls of the hollow bodies make Ving heat.

it possible to reduce considerably the number of die rings, and the push bench, therefore, can be much shorter and the pushing process is completed much sooner and with less power consumption.

Ifit is in line with the working operation, the tubular body supplied by the centrifugal casting drum is-irnmediately subjected to further treatment on the push bench, so as to utilize its cast- As a rule, however, the cast hollowA 19 bodies are put into a heating furnace where they are protected against cooling down and where also their heat is equalized/against each other. The bodies are takenout of the furnace as they are required and then conveyed to the push bench.

The new method also makes it possible to produce in a simple manner tubes or tubular bodies, the metal of which on the outside is of diierent kind from that onthe inside. These tubes, for instance, are corrosion-proof and heat-resisting tubes. Corrosion-proof tubes are tubes which on their outside and inside are immune to the touch of liquids or acids. Such tubes can readily be obtained by the centrifugalcasting process, as the special metals or constituents which character- .5 ize the desired tube diifer greatly in specific gravity from the ordinary iron or steel alloys or other tube material. If these special constituents have a higher specific gravity than the metal for the tubes, they are principally or exclusively de- 30 posited on the outside of the hollow body while vbeingcast in the centrifugal drum. If they have a lower specific gravity, they are precipitated on the inside ofthe tubes. The centrifugal drum must, of course, rotate with suiiicient speed to separate the materials in a satisfactory manner. Thus tubes may be produced which consist mainly of the required iron or steel alloy, but having outside and inside walls with quite different characteristics. In Figs. 8 and 9 the different layers of the tubular body are indicated by hatching differing from each other.

If heavymetals, such/as nickel or the like, are added to the alloy, the outside wall of the hollow body and tube derived from this will consist mainly or exclusively of nickel or the like. If a light metal, such as for example aluminium, chromium, zinc, tin or the like, is used in large quantities the ins'ide wallof the resulting tube will have a layer of the light metal used.

Such tubes have hithertofore been produced by' Lcoating the outside or inside of the tube of iron,

steel or other metal afterwards with the required material, but this method is much more expensive and not. so satisfactory. 5.- Corrosion-proof tubes may also be produced in the same manner for other purposesrthan to protect them against liquids or acids. Due to their great strength they can advantageously be used as drill pipesY and casings in oil drilling operations, and also as sludge pipes. Instead of reducing the thickness of the wal of the sleeve by passing them through die rings, they may b e pushed between rollers I of round or oval pass.' The' oval pass reduces the -friction between work piece ,and mandrel bar, so that thereby the otherwise frequent snapping of! of the closed bottom is avoided. The Ioval passes are replaced against each other for degrees. The rollers should not be specially ,driven but set 70 in rotation by the movingtubular body. The various sets of rollers may consist of 2`, 3 or 4. rollers. -The push bench also may alternately be provided with'die rings and rollers as described above. so that the-tubular body after having 7 moreandmnreormos'eandlelsi'irmiy' passeda die ringtravelsthroughasetofrollers, whereupon it on to a die ring again. and so forth.

Itisofadvantagetousehollowmandrel bars and hollow mandrel shafts. for producing large tubesinorderto reducetheweightandalsoto prevent the mandrel barsnfrom cracking as far as possible, owing to unequal cooling down and heating respectively. On account of the reduced weight of the hollow mandrel bars and mandrel shafts, besides, the accelerated masses in the A push bench and in thepolishing mill are reduced. The hollow mandrel bars as well as the hollow mandrel shafts, which move the mandrel bar forwards, are preferably made of thick-walled seamless tubes of carbon steel or alloyed steelf The tubes of unequal constituents of material may be used for producing sheet plate. the one wall of which is ofdiere'nt property to that of the other wall.' Such sheetlplate is hitherto produced thus that for example a hot nickel plate-is placed upon an iron plate and this iron plate is covered by a second nickel plate; all these plates are in hot condition. Thereuponthis parcel cf sheets or plates is rolled out between Through the pressureoftherollsthe Aliinedwitlieacliotherl atthesamstime down to thinner thickness. The contact layers of plate.however,isoftenunsatisfactory. Butifsuchplateisproducedfroma tubularbo obtainedbythecentrifugalcastingproce'ssa'nd afterwards stretched out on the push bench, the contact of the various constituents of material is an absolutely hrm one, as they are practically cast together to a whole. Buch sheet plate, therefore, will never split or its outer layer peel off.

What I claim is:-

1. In the manufacture of seamless tubes, the steps of forming an open ended hollow' ingot by centrifugal casting, closing one end of said inaot while. the latter is still in the casting apparatus. and subjecting the thus for/med ingot to a push bench drawing process to produce an elongated thin-walled tube.

2. In the manufacture of seamless tubes. the steps of-forming an open ended multistrata hollow ingot by centrifugal casting. closing one end of said ingot while the latter is still in the casting apparatus, and subjecting the thus formed ingot to a push bench drawing proces to produce an elongated thin-walled tube. A 

